.flex {
    display: flex;
}
.align_item {
    align-items: center;
}
.flex_center {
    align-items: center;
    justify-content: center;
}
.flex_wrap {
    flex-wrap: wrap;
}
.pop-up {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(0,0,0,.4);
}